Abstract LB-175: β-Escin inhibits NNK-induced lung adenocarcinoma formation in A/J mice by suppressing ALDH1A1 positive cells; and RhoA/Rock induced invasion of human lung cancer cell growth.

Abstract

Abstract Lung cancer is the leading causes of cancer deaths. β-Escin a triterpene saponin isolated from horse chestnut (Aesculus hippocastanum) seeds, had tested on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung adenoma and adenocarcinoma formation in female A/J mice and its possible mode of action was evaluated using human lung cancer cell lines (H460 and H2126). For bioassay, at 6 weeks of age, mice were randomized and fed control AIN-76A modified diet. At 7 weeks of age (25 mice/group) intended for carcinogen treatment received one dose of 10 μmol NNK /mouse by i.p. injection. Three weeks after the NNK treatment, groups of mice fed either control or experimental diets containing 500 ppm β-Escin. Mice were continued on the respective diets and killed at 20 weeks (10 mice/group) and/or 36 weeks (15 mice/group) after NNK-treatment for lung tumor evaluation by histopathological methods. Administration of 500 ppm β-Escin significantly suppressed lung tumor (adenoma+adenocarcinoma) formation by >40% (p<0.0015), at 20 weeks and 53.3% (p<0.0001), at 36 weeks. Importantly, β-Escin showed NNK-induced lung adenocarcinoma inhibition by 65% (p<0.001), at 20 weeks and by 53% (p<0.0001) at 36 weeks. These results suggest that β-Escin inhibits the NNK-induced lung tumor and more so by suppressing adenocarcinoma formation. Immunohistochemistry analysis revealed that lung tumor harvesting from mice exposed to β-Escin showed significantly reduced ALDH1A1 expression when compared to control lung tumors. Since ALDH1A1 is a putative lung cancer stem cell marker and associated with therapeutic resistance. Furthermore, in Aldefluor assay using FACS analysis of lung cancer cell lines treated with different concentrations of β-Escin (0-40 µM) revealed that the subpopulation of cells with elevated ALDH activity has significantly inhibited by ∼60-85%. Also, β-Escin induced p21 levels and suppressed Rho A and Rock protein expression in H460 and H2126 cell lines and NNK-induced lung tumors. Our findings for the first time suggest that β-escin inhibits tobacco carcinogen-induced lung tumor formation by modulating ALDH1A1 positive cells and RhoA/Rock pathway singling. {Supported by Kerley-Cade Endowment for Cancer Research} Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-175. doi:1538-7445.AM2012-LB-175